forked from 1b-agent/fieldcraft-upstream
solve.nonlinear follows a nonlinear static step in load increments: dead loads and prescribed displacements ramp with the load factor, a pressure follows the deformed faces (its load stiffness symmetrised so the supernodal Cholesky stays), the consistent tangent is refactored every iteration with an optional line search, and an increment converges on force, displacement and energy together. Increments start from the extrapolated last one, grow after fast convergence and are cut back on inversion, a non-finite or growing residual, an indefinite tangent or too many iterations; the step stops cleanly at the minimum increment, the increment cap or the Newton iteration limit. Elements are assembled in parallel in label order (same bits on any thread count). Results carry Cauchy stress, logarithmic strain, the increment history and a displacement frame per increment, which results.frame and the results panel show. Trusses, shells, beams, plane stress, incompatible modes, temperature and centrifugal loads are refused by name; couplings warn that they stay linear. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm